An insulating rod used for a gas insulated switchgear or the like is used for electrically insulating and supporting a conducting high-voltage conductor arranged in a metal container in which sulfur hexafluoride is encapsulated. As material used for the insulating rod, glass fiber reinforced plastics (GFRP) which are excellent for electrical insulating properties and mechanical strength are generally adopted. Sulfur hexafluoride is a gas medium excellent for insulating properties and arc-extinguishing properties. However, sulfur hexafluoride is decomposed by electric discharge occurring when current is interrupted, etc., reacts with adsorbed water, etc., inside the container, and hydrogen fluoride gas is resultantly generated. Therefore, the glass fiber forming the insulating rod is eroded by the hydrogen fluoride gas. As a result, the mechanical strength or surface resistance thereof may deteriorate. Accordingly, when the insulating rod formed of GFRP, and a breaker having an electric-discharge-generation portion or the like are installed together in the sealable container in which sulfur hexafluoride is filled, resistance characteristics of the insulating rod against hydrogen fluoride gas is required to be improved.
As methods of improving the hydrogen fluoride-gas resistance characteristics of the insulating rod, means for coating epoxy-modified polyimide resin, alumina-filled paint, or the like on a surface of the GFRP, and substitution of the GFRP by p-aramid fiber reinforced plastics (AFRP) reinforced by p-aramid fiber having excellent hydrogen fluoride resistance characteristics, etc., are proposed (for example, refer to Patent Documents 1 and 2).